A group 3-5 nitride semiconductor widely used for blue LEDs and so on and represented by the formula InxGayAlzN (0≦x≦1, 0≦y≦1, 0≦z≦1, and x+y+z=1) is usually grown on a substrate for growth. The substrate for growth (hereinafter referred to as “substrate”) is usually made of sapphire; the group 3-5 nitride semiconductor is epitaxially grown on the sapphire substrate by metalorganic vapor phase epitaxy (MOVPE) or the like.
As group 3-5 nitride semiconductors are widely used for LEDs, they have been required to have high light emission output.
As a light emitting device with high light emission output, a group 3-5 nitride semiconductor having no sapphire substrate has been proposed.
If a sapphire substrate is removed from a conventional group 3-5 nitride semiconductor light emitting device including sapphire substrate, group 3-5 nitride semiconductor layer with a GaN layer and formed on the sapphire substrate, and two electrodes formed thereon, heat release is not shielded by the sapphire substrate. Because of this, the light emitting device can be driven at a high current density and, therefore, is expected to have a high light emission output; and besides since electric current is not shielded by the sapphire substrate, whereby it becomes possible to produce a vertical light emitting device in which electrodes are provided to both ends of a group 3-5 nitride semiconductor layer, and therefore it is expected that the degree of freedom in the structures of light emitting devices is heightened.
At present, a study of a method for producing a group 3-5 nitride semiconductor having no sapphire substrate has been made. However, since a bulk crystal growth is difficult to attain, no method for industrially producing a free standing substrate, in particular, a conductive free standing substrate is in actual use; also, no method for producing a group 3-5 nitride semiconductor having a free standing substrate has been developed.
Instead, various methods for producing a group 3-5 nitride semiconductor, in which the group 3-5 nitride semiconductor is grown on a sapphire substrate and both are then separated, have been proposed (see JP-W No. 2001-501778 and JP-A 2001-176813).
In the methods disclosed in these references, however, it was not possible to separate the group 3-5 nitride semiconductor and the substrate, and no light emitting device with sufficient light emission output was obtained due to damage to the group 3-5 nitride semiconductor caused at its separation step.